Based on the underlying compatibility of the production processes (wet laying), “tissue” production is counted among the paper making techniques. The production of tissue is distinguished from paper production by its extremely low basis weight of normally less than 65 g/m2 and its much higher tensile energy absorption index. The tensile energy absorption index is arrived at from the tensile energy absorption in which the tensile energy absorption is related to the test sample volume before inspection (length, width, thickness of sample between the clamps before tensile load). Paper and tissue paper also differ in general with regard to the modulus of elasticity that characterizes the stress-strain properties of these planar products as a material parameter.
A tissue's high tensile energy absorption index results from the outer or inner creping. The former is produced by compression of the paper web adhering to a dry cylinder as a result of the action of a crepe doctor or in the latter instance as a result of a difference in speed between two wires (“fabrics”). In the latter technique, often referred to as “(wet) rush transfer”, for instance the forming fabric of the paper machine is moved at greater speed than that of the fabric to which the formed paper web is transferred, for instance a transfer fabric or a TAD fabric (through air drying), so that the paper web is somewhat bundled when it is taken up by the transfer fabric. Many prior art documents (e.g. EP-A-0 617 164, WO-94/28244, U.S. Pat. No. 5,607,551, EP-A-0 677 612, WO-96/09435) refer to this as “inner creping”, when they describe the production of “uncreped” tissue paper by rush transfer techniques. The inner and outer creping causes the still moist, plastically deformable paper web to be internally broken up by compression and shearing, thereby rendering it more stretchable under load than uncreped paper. Most of the functional properties typical of tissue and tissue products result from a high tensile energy absorption index (see DIN EN 12625-4 and DIN EN 12625-5).
Typical properties of tissue paper include the ready ability to absorb tensile stress energy, their drapability, good textile-like flexibility, a high specific volume with a perceptible thickness, as high a liquid absorbency as possible and, depending on the application, a suitable wet and dry strength as well as an interesting visual appearance of the outer product surface.
Softness is an important property of tissue products such as handkerchiefs, cosmetic wipes, toilet paper, serviettes/napkins, not to mention hand or kitchen towels, and it describes a characteristic tactile sensation caused by the tissue product upon contact with the skin.
Although the term “softness” is generally comprehensible, it is extremely difficult to define because there is no physical method of determination and, consequently no recognized industrial standard for the classification of different degrees of softness.
To be able to detect softness at least semi-quantitatively, softness is determined In practice by means of a subjective method. To do so, use is made of a “panel test” in which several trained test persons give a comparative opinion.
In simplified terms, softness can be subdivided into its main characteristics, surface softness and bulk softness.
Surface softness describes the feeling perceived when e.g. one's fingertips move lightly over the surface of the sheet of tissue. Bulk softness is defined as the sensory impression of the resistance to mechanical deformation that is produced by a tissue or tissue product manually deformed by crumpling or folding and/or by compression during the process of deformation.
One method for increasing bulk softness of tissue paper as taught by WO 96/25557 involves
a) wet-laying an aqueous slurry containing cellulosic fibres to form a web
b) applying a water soluble polyhydroxy compound to the wet web, and
c) drying and creping the web (wet web addition method).
It is further known from U.S. Pat. No. 4,764,418 that some humectants such as polyethylene glycol contribute to the softness of tissue products if they are applied to a dry web.
The use of humectants, such as polyhydroxy compounds, in highly concentrated form, as softeners however, has the disadvantage that the humectant may, upon contact, draw too much moisture from the skin, for instance when blowing one's nose with a tissue handkerchief. Moreover the softening effect is not yet satisfactory.
WO 96/24723 teaches increasing the surface softness of tissue paper by applying discrete deposits of a water free lotion composition containing an oil and a wax. Since however, due to its solid consistency, the treatment composition remains on the surface of the tissue paper, it cannot contribute to bulk softness. Further, water-free lotion compositions based on waxy or oily materials often feel unpleasantly greasy or oily.
Moreover, water-free lotions such as the one in WO 96/24723 often do not feel particularly pleasant to the skin.
EP A 1 029 977 relates to a composition for treating paper products, such as tissue products, comprising between 30 and 90% by weight of oil, between 1 and 40% by weight of wax, between 1 and 30% by weight of an emulsifying agent and between 5 and 35% by weight of water. These lotion compositions are based on W/O emulsions, are solid or semisolid at 30° C., and remain primarily at the surface of the tissue paper, although they penetrate the tissue paper somewhat more than the solid composition of WO 96/24723.
DE 199 06 081 A1 discloses emulsions containing (a) 5 to 25% by weight polyol poly-12-hydroxy stearate, (b) 50 to 90% by weight waxy esters, and (c) 5 to 25% by weight waxes. This document further contains examples describing the treatment of tissue papers with W/O emulsions as defined above containing about 20 to 25% water. These compositions are solid or semisolid at 30° C. (Example 1 corresponds to lotion F of EP A 1 029 977) and demonstrate the same penetration behavior as described above for the lotions of EP A 1 029 977.
However, tissue papers treated with water-in-oil (W/O) lotions often float on the water for a longer time and cannot be flushed down, if they are to be disposed in a toilet. This is a serious disadvantage, in particular for lotioned toilet papers which are becoming increasingly popular due to their softness and pleasant feel on the skin of the user.
WO 97/30216 discloses a softening lotion composition for treating tissue. The composition is aqueous and liquid, and includes as active ingredients    (a) one or more saturated straight fatty alcohols having at least 16 C atoms in a preferred amount of 35 to 90% by weight,    (b) one or more waxy esters having a total of at least 24 C atoms in a preferred amount of 1 to 50% by weight,    (c) optionally non-ionic and/or amphoteric emulsifiers, preferably oil-in-water emulsifiers, and    (d) optionally 0 to 50% mineral oil.
The lotion composition comprises 1 to 50% by weight active ingredients and consequently 50 to 99% by weight of water. According to the teaching of WO 97/30217, this aqueous composition is combined with a quaternary ammonium compound.
If such high water content lotions are applied to tissue paper, they can strongly affect the strength properties (dry strength or wet strength, if additional water, e.g. from body fluids is absorbed by the tissue paper).
WO 02/057547 A2 relates to a lotioned fibrous web, in particular tissue paper web having a short water absorption time. This web is treated with a lotion composition based on an O/W emulsion comprising    A) at least one oil    B) an (O/W) emulsifier or (O/W) emulsifier combination, and    C) 6 to 35 wt.-% of water, based on the total weight of the lotion composition.
The oil component may be selected from glycerides, natural plant oils, dialk(en)yl ethers, dialk(en)yl carbonates, hydrocarbon-based oils, waxy esters and silicon oils. The specific combination of hydrocarbon-based oils, such as mineral oil and fatty ester emollients is not disclosed. On a concrete level, this international application also pertains to a lotioned tissue paper wherein the lotion comprises as main components 5.3 wt.-% polyglyceryl poly(12-hydroxystearate) (Dehymuls® PGPH), 5.3 wt.-% lauryl glucosid, 3.0 wt.-% glyceryl stearate, 30.0 wt.-% cocoglyceride, 30.0 wt.-% di-N-octylcarbonate, 1.5 wt.-% bisabolol and 4.0 wt.-% glycerol. This lotion is also disclosed as “composition 1” in WO 02/056841.
Although this lotion shows a good stability under usual conditions, stability problems may occur if it is stored for very long times or at higher temperatures. Moreover, it was noted that specifically the incorporation of plant extracts may cause an undesired coloring which lowers the whiteness (brightness) of tissue paper treated therewith. In addition, some customers perceived an undesired smell if this lotion was stored over a longer period of time.
In view of the above, one object of the present invention involves providing a lotion-treated toilet paper that overcomes the disadvantages of prior art formulations.
In a first aspect, the present invention is intended to provide a lotioned toilet paper which can be easily disposed of in a toilet, since it does not float on the water for long.
In a further aspect, the present invention seeks to provide a lotioned toilet paper, the strength properties of which are not greatly deteriorated by the application of lotion.
A further technical object of the present invention is to provide a lotioned toilet paper web which feels very pleasant to the skin and is not oily or greasy to the touch.
Moreover, the present invention also aims at providing a lotioned toilet paper web which shows an enhanced degree of whiteness (brightness).
It is one further technical object of the present Invention to provide a toilet paper treated with a lotion composition that can be applied at relatively low temperatures.
Finally, it is one further technical object of the present invention to provide a toilet paper treated with a lotion composition wherein said lotion composition shows a suitable, in particular improved balance of critical properties including stability, softness and/or sensory impression, compatibility with plant extracts and application temperature.
Further technical objects may become apparent to a skilled person when studying the following description.